It is known that an organism that lives under low temperature conditions produces an ice-crystallization inhibitor such as an antifreeze protein and uses such an ice-crystallization inhibitor to protect its cells from freezing. Hereinafter, an antifreeze protein is referred to as “AFP”. An AFP is a protein which exhibits characteristics such as thermal hysteresis, and can inhibit an aqueous solution from freezing by controlling the structures of ice-crystals. AFPs have been found in organisms such as a fish, an insect, a plant, a fungi and a microorganism.
In the past, AFPs have been found in fish such as a Cottidae, an insect such as a mealworm, a microorganism such as Flavobacterium, and the like, and the AFPs have a high activity for inhibiting ice-crystallization (Patent Documents 1 to 3). In addition, AFPs also have been found in a plant such as a winter rye and a carrot (Non-patent Documents 1 and 2).
Furthermore, AFPs derived from basidiomycete fungi such as Typhula ishikariensis and Flammulina velutipes KUAF-1 are known (Patent Documents 4 and 5).
Recently, there was an attempt at using AFPs for maintaining the quality of a frozen confection product and a frozen food, such as an ice cream, by industrially utilizing the above-described properties (Patent Documents 6 and 7).